Siren Control Module (SCM)
The siren is used as a sound source for the alarm function. The siren is mounted under the plenum on the passenger side. The siren is available with or without an internal vehicle tilt sensor. The type of siren mounted in the vehicle is market and customer dependent.
The siren sounds if the power supply is cut or if communication with the central electronic module (CEM) fails while the alarm is activated. The siren contains an internal battery which is charged when the ignition is on. This battery has a capacity for 10 alarm cycles. The battery service life is limited and depends on the local climate. The siren must be replaced regularly. The battery cannot be replaced by itself. The alarm cause can be read from VADIS. This states what caused the alarm.
If the vehicle is equipped with a siren with a vehicle tilt sensor, the sensor is integrated into the siren. The vehicle tilt sensor reacts to changes in the angle of lean of the vehicle and transmits a signal to the central electronic module (CEM). The aim is for the alarm to be triggered if somebody attempts to steal a wheel for example.
While the vehicle tilt sensor is mounted in the siren it is counted as a separate unit. If the vehicle tilt sensor indicates that the vehicle is about to be raised, the vehicle tilt sensor sends a signal to the Central electronic module (CEM), which in turn, transmits an activation signal to the Siren control module (SCM). The Siren control module (SCM) cannot trigger an alarm by itself.
The siren is powered via a fuse from the central electronic module (CEM) The siren is grounded in the engine compartment.